This application claims the priority of Japanese Patent Application No. 7-166850 filed on Jun. 8, 1995 which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a film initial-advance apparatus for a camera and, more particularly, to the structure of a film initial-advance apparatus for reciprocating a feeding claw by utilizing the rotating driving force of a gear train such as a planet gear for the initial advance of a film.
2. Description of the Related Art
A film initial-advance apparatus for a camera is an apparatus for winding a predetermined amount of the forward end of a loaded film around a take-up spool and setting the film ready for photographing before feeding the film by the amount equivalent to one frame. FIGS. 5 and 6 show a conventional film initial-advance apparatus.
FIG. 5 is a bottom view of the apparatus and FIG. 6 shows the apparatus seen from the back lid side of the camera. In FIG. 5, a fork gear 2 which engages the take-up shaft of a film patrone (represented by the reference numeral 1 in FIG. 6) and a rewinding gear 3 which meshes with the fork gear 2 are provided on the right-hand side, and a spool 5 for taking up a film 4 is provided on the left-hand side. The pinion 6 of a motor is connected to the spool 5 via a plurality of gears, and a planet gear mechanism including a sun gear 7 and a planet gear 8 meshes with the pinion 6. The planet gear 8 slides along a guide groove 9.
One-tooth sprocket 11 having a pawl tooth 10 is integrally provided with an initial feeding gear 12 in such a manner that the pawl tooth 10 engages a perforation 13 (FIG. 5) of the film 4. Since the planet gear 8 slides along the guide groove 9 in accordance with the direction of rotation, the planet gear 8 selectively meshes with the rewinding gear 3 or the feeding gear 12.
According to the above-described structure, when the spool 5 is rotated clockwise by the motor, the sun gear 7 is rotated in the same direction and the planet gear 8 is thereby rotated counterclockwise in FIG. 5. The planet gear 8 then moves to the position indicated by the solid line and meshes with the initial feeding gear 12 so as to rotate the one-tooth sprocket 11 clockwise. By the rotation of the one-tooth sprocket 11, the pawl tooth 10 engages the perforation 13, thereby feeding the forward end of the film 4 toward the spool 5, and the fed film 4 is taken up by the spool 5. On the other hand, if the motor is reversely rotated when the film 4 is fully exposed, the sun gear 7 is reversely rotated, and the planet gear 8 moves to the position indicated by the broken line so as to mesh with the rewinding gear 3. In this case, the fork gear 2 is rotated counterclockwise, thereby rewinding the film 4 into the patrone 1.
In the above film initial-advance apparatus, however, there is a problem that since the pawl tooth 10 engages a perforation 13 of the film 4 while the pawl tooth 10 is being rotated by the feeding gear 12, the time during which the direction of movement of the pawl tooth 10 and the direction of feed of the film 4 agree with each other is short, so that the film feeding operation is not always reliable. In addition, the perforation 13 is sometimes deformed or broken by the pawl tooth 10.
To solve this problem, an apparatus (U.S. Pat. No. 5,136,313) for reciprocating a feeding claw in the direction of film feeding, as shown in FIG. 7 is put to practical use. In this apparatus, a spool cam 16 having a projection 15 is attached to the bottom portion of a spool 14 which serves as a take-up shaft. A film feeding member 18 is provided with a claw 17 which engages the perforation 13 of the film 4, and the feeding member 18 is guided by a pin 19 which slides along a guide groove 20, as shown in FIG. 7.
The feeding member 18 is also provided with a first driving lever 22 and a second driving lever 23 with the spool cam 16, which is situated slightly below the feeding member 18, therebetween. The first driving lever 22 provided with a projection 25 is connected to the feeding member 18 via a leaf spring 24 so that the lever 22 may be withdrawn below. The second driving lever 23 having a cam surface 27 which comes into contact with the projection 15 of the spool cam 16 is rockably supported by a shaft 26.
According to this structure, the spool 14 rotates and the projection 15 of the spool cam 16 below the spool 14 engages the projection 25 at the time of the initial advance of the film 4, so that the feeding member 18 moves to the left-hand side in FIG. 7. On the other hand, when the projection 15 engages the cam surface 27 of the second driving lever 23, the second driving lever 23 rotates around the shaft 26, so that the feeding member 18 returns to the right-hand side in FIG. 7. After the film 4 is fed, the first driving lever 22 withdraws below in synchronism with the movement of the film 4, so that the projections 15 and 25 are released from each other and the reciprocating movement of the feeding member 18 is stopped.
In such an apparatus of a reciprocating movement system, however, the structure for the initial advance of the film 4 is complicated and the apparatus costs high. In addition, since the driving members for initial advance are disposed below the spool 14, it is necessary to dispose the main gear train (reference numerals 3, 6, 7, 8, etc. in FIGS. 5 and 6) for film feeding above the spool 14, which makes the structure so complicated that it is difficult to apply the apparatus for a low-cost camera.